1. Field of the Invention
This invention relates to a developing device, and more particularly to a developing device of simple construction for developing an exposed film loaded in a film magazine.
2. Description of the Prior Art
It has been known in the art to develop an exposed film for still cameras while the film is loaded in the film magazine. Some examples of such a simple developing device are disclosed in Japanese Patent Laid-open Nos. 95835/1973 and 3986/1967.
In this type of developing device, the film magazine in which the film is fully taken up on the film wind-back spool after all frames of the film have been exposed is dipped in a developer liquid and the film wind-back spool is rotated back and forth to develop the film.
In the development process by use of this type of developing device, the film wind-back spool must be continuously rotated back and forth at a substantial speed so that the developer liquid sufficiently circulates in the film magazine and uniformly contact the whole surface of the film to produce uniform development. Further, the rotation of the film wind-back spool must be continued for at least a few minutes. According to experiments by the inventors, it takes about three minutes for development and 3 or 4 minutes for fixing, the spool must be rotated at a speed of at least one revolution per second.
In the conventional developing device of the above described type, a rotating rod which has a forked end to be engaged with the engaging portion of the film wind-back spool within the spool shaft is used for rotating the spool. It is, however, difficult to continuously rotate the spool for a long time by use of this sort of rotating rod. For instance, in primary schools and junior high schools in which this type of developing device is particularly appreciated as a teaching device, the strength of the children's fingers is not sufficient to achieve smooth rotation of the rotating rod and there is a high probability of resulting uneven development. According to tests by the inventors in which films were developed by 50 junior high school students by use of the above described type of simple developing devices, about 30% of the films were unevenly developed. About a half of the films unevenly developed were almost useless.
The reason for the above test results is believed to be that the developer liquid was not uniformly stirred because of insufficient rotation speed and shortness of rotation time. As a result the developer liquid was not sufficiently circulated in the film magazine and therefore did not come into uniform contact with the surface of the film.
Further, in the above mentioned type of development devices, it has been proved desirable to rotate the film wind-back spool ten to twenty times in the direction to tighten the film wound thereon and then several times in the direction to loosen the film wound thereon. Since the rotation of the spool in the direction to loosen the film is precluded by the film expanding in the film magazine, the film wind-back spool is mainly rotated in the direction to tighten the film to perform the development. On the other hand, since the right hand is usually used to rotate the spool and accordingly it is easier to rotate the spool clockwise, the film magazine should preferably be supported in such an orientation that the direction of the spool rotation to tighten the film becomes clockwise. The ordinary cylindrical film magazine which is popular in still cameras has a film wind-back spool one end of which is projected out of one end of the film magazine. The projected end of the spool in the film magazine is usually projected out of the lower end of the film magazine when the film magazine is put in the left side of the camera with the back cover opened and the film is pulled out of the film magazine and engaged with a film take-up spool in the camera located on the right side of the camera. Therefore, the film magazine should preferably be supported with the projected end of the spool directed downward in order that the direction of the spool rotation to tighten the film may become clockwise to make it is easy for the right hand to rotate the spool.
In the conventional developing device, however, if the film magazine is put into the developing tank with the projected end of the spool directed downward (as shown in FIG. 1 of Japanese Patent Publication No. 11433/1966), the developer liquid around the projected spool is not made use of for development, which is economically disadvantageous.